Scanning transmission techniques

NEXAFS experiments on NOM can be conducted in several modes that differ in the type of detected particle and objectives of the experiment transmission (X rays transmitted through the sample), fluorescence (fluorescent X rays due to absorption of the X-ray beam), or electron yield (photo-emitted electron) (Sparks, 2003). Alternatively, the techniques can be divided into full-field applications such as transmission X-ray microscopy (TXM) and X-ray photoemission electron microscopy (PEEM), in comparison to scanning techniques such as scanning transmission X-ray microscopy (STXM) and scanning photoemission microscopy (SPEM) that provide spatial information of elemental forms. 

Feser, M., Carlucci-Dayton, M., Jacobsen, C., Kirz, J., Neuhausler, U., Smith, G., and Yu, B. (1998). Applications and instrumentation advances with the Stony Brook scanning transmission x-ray microscope. In X-Ray Microfocusing Applications and Techniques, McNulty, I., ed., Proceedings of Society of Photo-optical Instrumentation Engineers, San Diego, CA, Vol. 3449, pp. 19-29. 

The most facile entry into surface complexation involved hydrolysis of ester-terminated dendrimers (derived from Michael additions of surface NH2 groups to methyl acrylate) with stoichiometric amounts of alkali-metal hydroxides. In this manner, salts of Na+, K +, Cs+, or Rb+ were readily obtained (Scheme 31) as white hygroscopic powders. Dilute solutions of the sodium salts allowed direct observation of the individual dendrimer molecules by scanning transmission electron microscopy without the use of staining techniques [79-81]. Elemental analyses showed that essentially stoichiometric exchanges with divalent cations such as Ca2+ could be performed [164],... 

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